Combination weighing systems of the type having a plurality of circularly arranged weigh hoppers are well known. For example, the Henry et al. U.S. Pat. No. 4,418,771 discloses a system wherein a predetermined weight of product is made up of individual articles of varying weights. In the Henry method and apparatus, the predetermined weight is reached by selecting the product stored in a combination of a predetermined number of storage cups. Quantities of the product having targeted weights are distributed to a plurality of scale-controlled hoppers for accurate weighing. The weighted product is fed from each of the scale-controlled hoppers to a plurality of storage cups associated with each of the hoppers, and the product weight associated with each storage cup is registered. Specific combinations of storage cups are tested to determine whether the combined product weights therein add up to make the desired weight, within acceptable limits. The first combination found to make the weight is used, and the appropriate storage cups are emptied to a container for receiving the product. The appropriate storage cups are refilled from the scale, and the process repeats. When none of the combinations of the preselected number of storage cups include a total product weight within the acceptable limits, the limits are broadened and the cycle repeats. The weighing system includes a programmed microprocessor for controlling operation thereof, for providing the combination to be tested, for calculating the combined weights, and for determining whether the combined weight falls within the acceptable limits. A distributor for the product includes a reversing rotating portion for preventing clogging of the product at openings provided for chutes connecting the distributor to the scale-controlled hoppers.
A more recent approach to an improved combination weigher is disclosed in the U.S. Pat. No.5,211,253 of Russel Davis which is assigned to the same assignee as the present application and which is incorporated herein in its entirety by reference. As disclosed by Davis, the apparatus comprises means including a plurality of balances each of therefrom to contribute to a delivery. The apparatus also includes means for recording a predetermined target weight and control means for determining which of the balances are in a ready or stable state. Means are also provided for generating the values of combinations of weights on the balances which are in the ready sate and for comparing the values with the predetermined target weight and for selecting a combination of balances to be unloaded to deliver a collection of articles having a combined weight which most nearly approximates the target weight. In practice, it may be desirable to select those scales having a combined weight which is at least equal to the predetermined weight to avoid any underweight packages. The apparatus also includes package positioning and signal generating means such as a packaging machine for positioning a package to receive a collection of articles from the selected balances and for generating a signal to indicate that a package is positioned to receive the articles from the balances. Means for unloading the balances of the selected combination for delivery of the product contained therein to a properly positioned package are also provided. Means for generating the values of combinations of weights on the balances which are in the ready state including the originally selected balances and any balances which have reached a ready state subsequent to a first comparison are actuated for comparing the values with the predetermined target weight. In this manner, all of the ready balances are included in the comparison and a second selection having a weight which most nearly approximates the target weight is delivered to a package. Means are also provided for refilling those balances which have been unloaded.
Combination weighers as mentioned above also incorporate a distribution system for delivering solid flowable product to the plurality of scales. In such distribution systems, a cone shaped member is located directly above the infeeds for a plurality of feeders. In such devices a relatively deep pile of product may form on the cone shaped member. This pile of product then exerts an outward force on the product that causes the product to surge outwardly causing inconsistent or non-uniform feeding. The result is that there is a relatively large variance between the weights on the various scales. At times, such surges also lead to clogging of the product which requires a mechanism for preventing and/or breaking up any clogging or bridging which may occur. An example of an anti-clogging mechanism is disclosed in the aforementioned U.S. Pat. No. 4,418,771.
It has now been found that the performance of combination weighers can be improved by means of an improved distribution system of the type disclosed herein. Such systems provide a more uniform distribution of product, less variance in the weighed product, reduce the likelihood of clogging and thus obviate a need for an anticlogging mechanism. In addition, it is now believed that such systems may eliminate the need to rotate and/or vibrate the distribution cone and therefore, reduce the cost and complexity of the resulting combination weighers, minimize the need for maintenance and result in a more durable system.